"I have lived a long life and I have seen a few things. I walked away from the Last Great Time War. I marked the passing of the Time Lords. I saw the birth of the universe and I watched as time ran out, moment by moment, until nothing remained. No time. No space. Just me. I walked in universes where the laws of physics were devised by the mind of a mad man. I've watched universes freeze and creations burn. I've seen things you wouldn't believe. I have lost things you will never understand. And I know things. Secrets that must never be told. Knowledge that must never be spoken."
-The Doctor in the Rings of Akhaten
 
"I can see everything. All that is, all that was, all that ever could be."

"That's what I see. All the time. And doesn't it drive you mad?"
The Doctor and Rose in The Parting of the Ways